Adjust descriptions based on latest API changes

Author: rayluo

sample/client_credential_sample.py

@@ -38,7 +38,7 @@
 
 # Firstly, looks up a token from cache
 # Since we are looking for token for the current app, NOT for an end user,
-# notice we give account parameter as None (which is its default value, by the way).
+# notice we give account parameter as None.
 result = app.acquire_token_silent(config["scope"], account=None)
 
 if not result:

sample/device_flow_sample.py

@@ -34,8 +34,8 @@
 # The pattern to acquire a token looks like this.
 result = None
 
-# If your device-flow app does not have any interactive ability,
-# you can completely skip the following cache part. Here we demonstrate it anyway.
+# Note: If your device-flow app does not have any interactive ability, you can
+#   completely skip the following cache part. But here we demonstrate it anyway.
 # We now check the cache to see if we have some end users signed in before.
 accounts = app.get_accounts()
 if accounts: